In the manufacture of semiconductor devices, a required device is fabricated by repeatedly performing a variety of types of processes, such as film forming processing and etching processing, on a semiconductor wafer. In recent years, in line with the needs of high speed, fine wiring pattern, and higher integration of semiconductor devices, a wiring needs to have low resistance (improved conductivity) and improved tolerance to electromigration.
For this reason, copper (Cu) having higher conductivity (lower resistance) and higher tolerance to electromigration than aluminum (Al) or tungsten (W) are used as materials for wirings.
A technology has been used in which a barrier film made of tantalum (Ta), titanium (Ti), tantalum nitride (TaN), or titanium nitride (TiN) is formed on the entire interlayer dielectric film in which trenches or holes have been formed using a plasma sputter, that is, a physical vapor deposition (PVD) method. In this process, a Cu seed film is formed on the barrier film in the same manner using a plasma sputter, and the trenches or the holes are fully buried by performing Cu plating on the Cu seed film. A Cu thin film and a barrier film remaining on a surface of the wafer are removed by polishing and are processed using chemical mechanical polishing (CMP) processing to form a Cu wiring.
However, as the design rule of semiconductor devices gradually becomes more fine, the wettability of the Cu film for a barrier film is poor and PVD basically has low step coverage. Accordingly, it is difficult to soundly form the Cu seed layer within the trenches or the holes using PVD, and thus a void is generated in the Cu film when the trenches or the holes are buried with the Cu film.
In this aspect, a technology has been used in which an Ru film having an excellent wettability for Cu is formed on a barrier film made of Ta or TaN using CVD having basically excellent step coverage. Once the Ru film is formed on the barrier film the Cu is buried in the barrier film.
Furthermore, there has also been proposed a technology in which a Cu film is buried using ionized physical vapor deposition (iPVD) after the Ru film is formed using CVD as described above. Accordingly, the CVD-Ru film having excellent step coverage is thinly formed in order to increase the volume of the Cu film as much as possible and an iPVD film is formed at a relatively high temperature in order to increase the crystalline size of the Cu film, thereby being capable of making a Cu wiring have low resistance through a synergy effect. Furthermore, iPVD can obtain an excellent burial property even in the case of a fine trench because the overhang of a trench width can be suppressed by the etching action of Ar ions and the like.